BACKGROUND: Absence of enteral nutrition (EN) reduces hepatic mononuclear cell (MNC) numbers and impairs their functions. However, enteral refeeding (ER) for as little as 12 hours following parenteral nutrition (PN) rapidly restores hepatic MNC numbers. We hypothesized that changes in small intestine and portal vein blood flows related to feeding route might be responsible for this phenomenon. METHODS: In experiment 1, mice (n = 19) were randomized to Chow (n = 5), PN (n = 7) or ER (n = 7) groups. The Chow group was given chow ad libitum with intravenous (IV) saline for 5 days. The PN group was fed parenterally for 5 days, while the ER group was re-fed with chow for 12 hours following 5 days of PN. Then, small intestine and portal vein blood flows were monitored and hepatic MNCs were isolated and counted. In experiment 2, the effects of intravenous administration of prostaglandin E(1) (PGE(1)) on hepatic MNC numbers were examined in fasted mice for 12 hours. Mice (n = 28) were randomized to Control (n = 8), PG0 (n = 10), or PG1 (n = 10) groups. The Control group was fed chow ad libitum with IV saline, while the PG0 and PG1 groups were fasted for 12 hours with infusions, respectively, of saline and PGE(1) at 1 microg/kg/minute. Blood flows and hepatic MNC numbers were examined. RESULTS: Experiment 1: ER restored PN-induced reductions in small intestine and portal vein blood flows and hepatic MNC number to the levels in the Chow group. Small intestine and portal vein blood flows correlated positively with hepatic MNC number. Experiment 2: Fasting decreased small intestine and portal vein blood flows and hepatic MNC number. However, PGE(1) restored portal vein blood flow to the level of the Control group, and moderately increased hepatic MNC number. There was a positive correlation between portal blood flow and hepatic MNC number. CONCLUSIONS: Reduced small intestine and portal vein blood flows may contribute to impaired hepatic immunity in the absence of EN. ER quickly restores hepatic MNC number through recovery of blood flow in both the small intestine and the portal vein.
BACKGROUND: Absence of enteral nutrition (EN) reduces hepatic mononuclear cell (MNC) numbers and impairs their functions. However, enteral refeeding (ER) for as little as 12 hours following parenteral nutrition (PN) rapidly restores hepatic MNC numbers. We hypothesized that changes in small intestine and portal vein blood flows related to feeding route might be responsible for this phenomenon. METHODS: In experiment 1, mice (n = 19) were randomized to Chow (n = 5), PN (n = 7) or ER (n = 7) groups. The Chow group was given chow ad libitum with intravenous (IV) saline for 5 days. The PN group was fed parenterally for 5 days, while the ER group was re-fed with chow for 12 hours following 5 days of PN. Then, small intestine and portal vein blood flows were monitored and hepatic MNCs were isolated and counted. In experiment 2, the effects of intravenous administration of prostaglandin E(1) (PGE(1)) on hepatic MNC numbers were examined in fasted mice for 12 hours. Mice (n = 28) were randomized to Control (n = 8), PG0 (n = 10), or PG1 (n = 10) groups. The Control group was fed chow ad libitum with IV saline, while the PG0 and PG1 groups were fasted for 12 hours with infusions, respectively, of saline and PGE(1) at 1 microg/kg/minute. Blood flows and hepatic MNC numbers were examined. RESULTS: Experiment 1: ER restored PN-induced reductions in small intestine and portal vein blood flows and hepatic MNC number to the levels in the Chow group. Small intestine and portal vein blood flows correlated positively with hepatic MNC number. Experiment 2: Fasting decreased small intestine and portal vein blood flows and hepatic MNC number. However, PGE(1) restored portal vein blood flow to the level of the Control group, and moderately increased hepatic MNC number. There was a positive correlation between portal blood flow and hepatic MNC number. CONCLUSIONS: Reduced small intestine and portal vein blood flows may contribute to impaired hepatic immunity in the absence of EN. ER quickly restores hepatic MNC number through recovery of blood flow in both the small intestine and the portal vein.